This invention relates to cam cleat devices used to grip rope, lines, or the like. More particularly, but not by way of limitation, this invention relates to a cam cleat device for securely holding or gripping a rope having slight tension exerted thereon.
Cam cleat devices have been used in a wide range of applications for gripping or securing rope, lines or the like, hereafter simply referred to as rope, to prevent translational movement. As examples, cam cleat devices have been used to secure sailing ropes and mountian climbing ropes so that they do not move with respect to a reference position. When used for sailing and climbing, rope tension typically ranges from hundreds to thousands of pounds. In contrast, cam cleat devices are also used as part of therapeutic devices which hang or suspend a patient or a part of a patient's body. In therapeutic applications, rope tension typically varies from several pounds to hundreds of pounds.
Simplistically, a cleat device traps a rope between the end of a rotating arm and a stationary surface located a fixed distance from the axis of the rotating arm. When the rope is in tension relative to the cleat device, the pressure of both the end of the rotating arm and the stationary surface against the rope will restrain axial translation of the rope through the cleat device provided the diameter of the rope at the point contacted by the end of the rotating arm remains greater than the distance of closest proximity between the end of the rotating arm and the stationary surface of the cleat device.
A cam cleat device improves upon the design of the cleat device by substituting for the rotating arm a cam having an arcuate surface eccentrically disposed relative to the axis of rotation of the cam. The arcuate surface provides a greater contact area between the cam and the rope while the eccentric positioning of the arcuate surface compensates for changes in the rope diameter which may be caused by the relative tension placed on the rope.
The arcuate surface of the cam cleat can be smooth, ribbed or toothed. The toothed or ribbed surfaces are in the form of a bed of numerous teeth or ribs generally situated in parallel rows along the arcuate surface of the cam cleat with the rows running in a direction other than parallel to the direction of rope translational movement. Such surfaces are thought to aid in gripping the rope to restrain translational movement of the rope relative to the cam cleat device and to aid in removal of debris, such as ice or dirt, from the rope.
The cam cleat device is typically spring-loaded to force the cam cleat to rotate in the direction in which the distance between the arcuate surface and the stationary surface decreases (positive cam rotation). Increasing the tension of the rope relative to the cam cleat device pulls the cam in the direction of positive cam rotation causing the cam cleat device to grip the rope more tightly.
In order to release the rope to permit it to translate through the cam cleat device, the cam must be rotated in the direction in which the distance between the arcuate surface and the stationary surface increases (negative cam rotation). This is normally accomplished by reducing or reversing the direction of the tension on the rope with respect to the cam cleat device. However, release of cam cleat devices is known to occur with no apparent change in relative tension, particularly in activities of low, or slight rope tension, such as therapeutic devices.
There is therefore a need for a cam cleat device which overcomes this problem. The present invention is set forth below and solves the problem.